Stone is heavier, and therefore usually closer to the ground. Also, it is used to lay the foundations of a building. You'd rarely see wood on a ground floor, and stone on the next floor up. Just as an example. I like all the arches, and you have all the wood in the right places, but I'd change the places where you used the stone. Also, somewhere on here and on the official forum is a tutorial for colour matching. A lot of it is experimentation, using the colour wheel as a guide. It looks like it's stuck between modern and medieval. What style in particular were you going for?